1. Field of the Invention
This invention lies in the field of seismic geophysical prospecting. More particularly it is involved with vibratory sources, which are programmed by reference signals.
Still more particularly it is concerned with aerial coverage, currently known as Three Dimensional Mapping, or 3D seismic operations, in which a plurality of spaced apart seismic sources are used, recording into at least one common geophone line.
Still more particularly, the invention involves methods of separating, in the data processing, the seismic waves progressing separately from two simultaneous vibratory sources at spaced-apart points, to a common receiver.
2. Description of the Prior Art
In the prior art it has been the entire practice, in vibratory source operations, to use a single source recording into a plurality of receivers. Even though a plurality of vibratory sources may be used, so as to provide greater energy, all of the sources are placed close to each other, and all are synchronized to the same reference signal. Thus all of the seismic energy travels by a common path to the receivers or sensors.
More recently there has been some interest in the simultaneous use of a plurality of spaced apart vibratory sources each with a different reference signal. Silverman in U.S. Pat. No. 3,984,805 uses non-synchronized, non-phase-controlled spaced-apart vibrators, and separates the seismic components in the received signal on the basis of correlation with the separate reference signals. Anstey et al in their U.S. Pat. No. 3,885,225 uses separate reference signals in separate frequency bands, and separates the signal components in the received signal on the basis of correlation with the corresponding reference signals.
In this invention the method of separation of the seismic waves from the two or more sources is by a different method.